The dealership should be able to find the leak. That's incredible that you've taken it in 9 times and they still haven't looked hard enough for the leak to locate it. The easiest way to find the leak is to pull the carpet back some and look with a flash light while someone pours water over the entire roof, windshield, firewall, door and cowl. The three most likely problems are a windshield leak, improper sealing of the firewall, and a drain is disconnected from the sunroof. If you can remove the A-pillar trim from the vehicle you can look to see if it's wet. This is a quick way to tell if the sunroof drain is the problem or not.